Active-matrix type display devices comprising a plurality of pixels include a wiring substrate on which switching elements for driving the pixels are formed. The switching elements are each formed from, for example, a thin film transistor. Such a display device, in some cases, comprises a contact hole formed therein to connect an electrode of a switching element to another conductive material formed in a different layer on the wiring substrate.
On the other hand, in the same layer where the electrode of the switching element is formed, it is necessary to provide a space (margin) between the electrode of the switching element and other conductive materials in order to avoid the electrode of the switching element from contacting the other conductive materials.
In recent years, as the definition of display devices is increased, the width of the pixels tends to decrease. Therefore, the ratio between the width of the electrode and the margin in a pixel is becoming unneglectable.